so I just took the head off my sr20det and it's currently being rebuilt, my question is if I can get away with reusing the Pistons and all that the car was working fine until I broke a rocker arm and gave up, it was froze so I was unable to put it in time, when I removed the head there was 2 freeze plugs thingys on my 3rd piston which when I looked the spring above was loose, the top of the Pistons do have a some scratches from the freeze plug thingys , I'm currently saving but doing a full rehaul new Pistons and all that is out of my price range but if you guys could give me your opinions would it be safe just to put a new head gasket and new head and I'd be fine for a while so I can save a build my other motor?

You said your sr20det is currently being rebuild. Normally rebuilt means new rings and bearings. So having trouble following where your at.

If you removed your head and there was 2 "thingys" on top of your piston. You will probly want to pull at least that one out inspect the piston and wall.
You said your just going to get a new gasket and head. That sounds like the head is destroyed? Hard to imagine a head destroyed but the piston survived unless the rocker carved into say the cam journal area.

If the piston and wall didnt take damage you could most def. just slap on a new gasket and head. Id dump the oil and look for metal at least since it suffered a head destroying failure.

You can bolt down new gasket and head then do a leak down test to confirm your pistons and rings will at least "hold" compression. I suppose you'll need those parts anyways so its not like a waste to get to that point to do that test.

Pictures would help us help. If your walls are not damaged you might just need 1 piston. You don't have to replace them all nor do you have to replace anything that is serviceable.